@ideditor/location-conflation

location-conflation

🧩 Define complex geographic regions by including and excluding country codes and geojson shapes.

What is it?

Location-conflation is a tool for generating GeoJSON features by including and excluding other locations and shapes.

You can define a location set as an Object with include and exclude properties:

let locationSet = {
  include: [ Array of locations ],
  exclude: [ Array of locations ]
};

The "locations" can be any of the following:

• Strings recognized by the country-coder library. These should be ISO 3166-1 2 or 3 letter country codes or UN M.49 numeric codes.
  Example: "de"
• Filenames for .geojson features. If you want to use your own features, pass them to the LocationConflation constructor in a FeatureCollection - each Feature must have an id that ends in .geojson.
  Example: "de-hamburg.geojson"
• Points as [longitude, latitude] coordinate pairs. A 25km radius circle will be computed around the point.
  Example: [8.67039, 49.41882]

Usage Examples

const LocationConflation = require('@ideditor/location-conflation');
const myFeatures = require('./featurecollection.geojson');   // optional
const loco = new LocationConflation(myFeatures);

Southern Europe:

let result = loco.resolveLocationSet({ include: ['039'] });   // 039 = Southern Europe

Southern Europe and Northern Africa:

let result = loco.resolveLocationSet({ include: ['039','015'] });   // 015 = Northern Africa

Southern Europe and Northern Africa, excluding Egypt and Sudan:

let result = loco.resolveLocationSet({ include: ['039','015'], exclude: ['eg','sd'] });

The Alps, excluding Liechtenstein and regions around Bern and Zürich

let result = loco.resolveLocationSet({ include: ['alps.geojson'], exclude: ['li', [8.55,47.36], [7.45,46.95]] });

Other Fun facts

• This library is a wrapper around
  • Country-coder for world boundaries, and
  • Turf.js for geospatial union/difference functions
• Results contain an area property containing the approximate size of the feature in km²
  (This is helpful for sorting features)
• Results contain a stable id in the form +[included]-[excluded]
  (e.g. "+[015,039]-[eg,sd]")
• Results are cached, so if you ask for the same thing multiple times we don't repeat the expensive turf calls.

Prerequisites

• Node.js version 8 or newer
• git for your platform

Installing

• Clone this project, for example: git clone [e-mail]:ideditor/location-conflation.git
• cd into the project folder,
• Run npm install to install libraries

Building

• npm run build

License

This project is available under the ISC License. See the LICENSE.md file for more details.